Recently, the techniques for micronizing semiconductor devices have been advanced and there has been such a remarkable tendency that a semiconductor device has a three-dimensional structure. As a result, there has widely been used a technique which makes use of a silicide film formed on, for instance, the bottoms of trenches and holes, which are formed on or through a substrate, and the side walls thereof. For this reason, the need for the achievement of a high coverage characteristics (step-coverage characteristics) of such a silicide film with respect to these bottoms and sides has also become higher and higher.
As metals for forming such a silicide film, there have conventionally been used, for instance, Ti, Co and Ni. The sputtering technique has conventionally been used as a means for forming films of these metals, but a problem has arisen such that this technique is insufficient in the coverage characteristics of the resulting film with respect to the bottoms and sides of such trenches and holes as the micronization technique has been advanced and that the technique cannot cope with such circumstances.
For this reason, there has been developed a CVD technique in which a film is formed by gasifying a metal compound and introducing the gaseous metal compound into a film-forming apparatus. However, this CVD technique suffers from a variety of problems such that the technique uses an organometallic compound as a source of gaseous metal material and therefore, the resulting film thus formed is contaminated with a large quantity of impurities such as C, N and O, that the presence of such impurities would inhibit the silicide-forming reaction even if the resulting film is subjected to a heat-treatment to form a silicide and that it is difficult to form a silicide film starting from the metal film formed according to this CVD technique as compared with the formation thereof starting from the metal film formed according to the conventional sputtering technique.
In the meantime, a silicide film can be formed simply by the formation of a film according to the CVD technique if the film is formed by the technique at a high temperature (for instance, 500° C.), which permits the direct formation of a silicide film according to this technique, but it would be quite difficult to form a necessary and excellent silicide interface required for the production of, for instance, a semiconductor device. For example, in the case of Ni, an NiSi film permits the formation of an excellent low resistant interface, but a problem arises such that the film-forming process carried out at a high temperature would result in the formation of an undesired NiSi2 film and that it is impossible, for this technique, to form any flat low resistant interface. Moreover, a further problem also arises such that when forming a film at such a high temperature, the film-forming rate is increased, but the rate is determined by the feed of a raw material and accordingly, the resulting film is insufficient in the coverage characteristics.
Furthermore, when a semiconductor device is produced, a metal conductive film (such as a Cu film) is subjected to a hydrogen (or ammonia)-annealing treatment for the purposes of the improvement of the electrical properties of the metal conductive film by the removal of impurities such as carbon and nitrogen present in the resulting conductive film and of the improvement of the adhesion between a primary film and the Cu film (see, for instance, Patent Document 1 specified below). In this connection, such an annealing treatment would permit the reduction of the content of impurities such as carbon and nitrogen present in the film, but it never permits the removal of such impurities as oxygen likewise present in the film. For this reason, there has been desired for the development of an Ni film whose oxygen content is low or which is substantially free of oxygen and a method for forming the same.